A conventional factory automation (FA) system is shown schematically in FIG. 1. A plurality of workcells 1 of the FA system are connected to each other and to an upper controller (FA PC) 3 via a communication network 2. The following device control and information handling tasks are performed in the workcell 1:
Control of an industrial robot 4 and DI/DO devices 5
Control of an operation panel 6 that is an interface device for an operator
Collection, analysis, and storage of such information as workcell operation status, and communication with the other workcells 1 and the upper controller 3.
The above device control and information handling tasks are performed by the following devices:
I. A robot controller 7, for the control of the industrial robot 4
II. A programmable logic controller (PLC) 8, for the sequence control of the DI/DO devices 5
The PLC 8 performs the following operations:
Receiving, as DI signals, the statuses of the sensors provided in the devices
Determining output signals according to registered conditions
Controlling the actuators, valves, and relays provided in the devices by outputting DO signals
The DI/DO (digital-in/digital out) signals are digital signals that take two states: on and off.
III. FA personal computer 9
This device performs the following operations:
Controlling the operation panel 6 (namely, the display or handy terminal) provided for the interface with an operator
Collecting, analyzing, and storing various items of information
Communicating with the other workcells 1 and the upper controller 3
As shown in FIG. 1, the conventional workcell 1 has a plurality of control devices for device control and information handling. Therefore, the operation software inherent in the workcell 1 needs to be separated into a program written in a robot language that runs on the robot controller 7, a ladder chart that runs on the PLC 8, and a program written in an ordinary high-level programming language such as C language that runs on the FA personal computer 9. Consequently, the programs for many control devices used in one workcell 1 must be prepared independently. Further, the programming must be conducted so as to ensure that the robot 4 and the DI/DO devices 5 operate, when viewed as a whole, at high speed, in synchronization with one another and in asynchronization with one another.
FIGS. 2 and 3 show synchronized programs describing operations of the robot 4 and devices 1 and 2 according to prior art. A robot language program (FIG. 2) and a ladder chart (FIG. 3) need to be prepared for the robot controller 7 and the PLC 8, respectively.